1. Field of the Invention
This invention relates to headlamps for moving vehicles and, more particularly, to a high intensity lamp capable of selectively projecting multiple light colors.
2. Background of the Invention
Conventional sealed beam headlamps, used on automobiles, other high speed vehicles and off road vehicles, employ a filament to project white light through a clear, light-diffusing element, which is typically glass or plastic. Many competing objectives come into play in headlamp design. A high intensity lamp that clearly illuminates a highway far in front of a moving vehicle subjects oncoming traffic to the glaring brightness of the unconcealed filament under normal driving conditions. In the presence of fog, dust, snow, rain and/or smoke, the light projected from the headlamp tends to reflect back and obstructs the vision of the vehicle operator without illuminating in front of the vehicle sufficiently to make travel at high speed safe. Fog lamps, which project yellow light that has good penetrating capability in fog, dust, snow, rain and/or smoke, normally do not alone have the intensity to satisfactorily illuminate a roadway at high speeds with unobstructed visibility.
It has heretofore been common to provide both sealed beam white light lamps and fog lamps on the same vehicle. This requires mounting at least four headlamps, which is expensive from a manufacturing standpoint. This cost is ultimately passed on to the consumer. Further, the consumer must bear the burden of replacing twice as many headlights when the lights burn out.
As an alternative to providing separate fog and white light headlamps, a combination yellow and white light lamp is described in my application Ser. No. 653,437, entitled "Improved Vehicle Headlamp". While that particular light construction gives adequate illumination under both normal and adverse weather conditions, the vehicle operator may prefer to project only white or yellow light as conditions may dictate.